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Full text of "Handbook Of Chemical Engineering - I"

THE TRANSPORTATION OF LIQUIDS
129
being cleaned. A surface condenser may be placed in the suction pipe of the pump, provided there is a place below it for the condensate pump. It is arranged so that the water flows around the tubes, while the exhaust steam flows through the tubes. Only a small wet vacuum pump is then required to remove the condensate and the air. A better place for it is in the discharge pipe as this gives a greater suction head for the vacuum pump. This is much more costly on account of the high pressure for which it must be designed, but an obstruction in the discharge pipe is by far not so objectionable as one in the suction pipe.
Acid Pumps.—When an acid or other corrosive substance is to be handled by a pump no material should be used that is attacked by the substance. For this reason pumps may be constructed either wholly of brass, bronze, rubber or even stone ware, or wholly of iron or they may be merely bronze fitted, which means that certain working parts such as pistons, rods, pump pistons, etc., are made of bronze or bronze lined. In ordering bronze or brass-fitted pumps it should be clearly specified what parts should be made of bronze or brass. In an all-iron pump the pump cylinder is bored to size and has no lining. The valve seats and stems are made of malleable iron.
If the size permits it in a brass fitted pump the piston rod should be split in the cross head, and the steam piston rod should be made of steel. Brass at the high temperature in the steam cylinder is too soft to wear well.
Table 6 gives a very complete list of substances that may be handled by pumps and the materials of which the pump parts should be constructed.
TABLE 6.—MATERIALS FOR PUMP PARTS FOR HANDLING VARIOUS LIQUIDS
Column 2		Columns 4 and 6		Compositions of					
Condition		material		acid metal					
Con. Dil Ex. c.	Concentrated Diluted Extremely concentrated	AB AI AM BF	All bronze All iron Acid metal Brass fitted	Cu	Sn	Pb	Sb	Al	Tensile strength
				82 88	5 10	12 2		1	
		CI.	Cast iron						
Column 5		E	Enameled	90	Aluminum Bronze			10	45,000
valve service		HL	Hard lead						
		LB	High lead bronze	75	5	20	Light section		19,000
									
				80	5	15	Heavy section		15,000
R	Regular valve	MM	Monel metal						
L.O.	disc, etc. Large openings No ribs in scat	PB RF AL	Phosphor bronze Regular fitted Aluminum	M	H (Fo	85M r mine	13H water)	(Ant. lead)	
	Ball valve	Cu	Copper						
	Clapper Valve	Pb	Lead						
	Etc.	Sb	Antimony						
		SbPb	Antimonial lead			90	10	(For acid)	
		Sn	Tin						
									
The column numbers refer to the columns on pp. 130-134. For handling substances for which material E is specified, pumps made entirely of rubber would be most suitable. The American Hard Rubber Co., New York, N. Y., is developing such a line, which will include single and duplex direct-acting, steam pumps, power and centrifugal pumps, as well as piping, fittings and valves. Pumps handling foods or medicines must be kept clean and should preferably be all bronze.